Seawater minor chemical components

M.J. and Holland, H.D. (1978) Chemical exchange during hydrothermal alteration of basalt by seawater. I Experimental results for major and minor components of seawater. Geochim. Cosmochim. Acta, 42, 1103-1115. 

The seas are a source of aerosol (i.e. small particles), which transfer to the atmosphere. These will subsequently deposit, possibly after chemical modification, either back in the sea (the major part) or on land (the minor part). Marine aerosol comprises largely unfractionated seawater, but may also contain some abnormally enriched components. One example of abnormal enrichment occurs on the eastern coast of the Irish Sea. Liquid effluents from the Sellafield nuclear fuel reprocessing plant in west Cumbria are discharged into the Irish Sea by pipeline. At one time, permitted discharges were appreciable and as a result radioisotopes such as Cs and several isotopes of plutonium have accumulated in the waters and sediments of the Irish Sea. A small fraction of these radioisotopes were carried back inland in marine aerosol and deposited predominantly in the coastal zone. While the abundance of Cs in marine aerosol was refiective only of its abundance in seawater (an enrichment factor - see Chapter 4 - of close to unity), plutonium was abnormally enriched due to selective incorporation of small suspended sediment particles in the aerosol. This has manifested itself in enrichment of plutonium in soils on the west Cumbrian coast,shown as contours of 239+240p deposition (pCi cm ) to soil in Figure 3. 

Many models have been developed to estimate the thermodynamic activities of solutes in natural waters (e.g., see Millero, 1984). Of these, the ion pairing and specific interaction theories are the most widely used. A combined model that uses the Pitzer equations to represent specific interactions between ions, together with a thermodynamic description of chemical equilibria, has proved successful in estimating the activities of both major and minor components of seawater (Dickson et al., 1988 Harvie et al., 1984). 

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